The present invention relates to improvements in pulleys and like articles which are or can be made of a polymeric material, especially to improvements in articles which are manufactured in casting, extruding and like machines. More particularly, the invention relates to improvements in articles of the type having two coaxial tubular sections and a ring-shaped intermediate section which is integral with the tubular sections. If an article of the just outlined character is used in a belt transmission or the like, one of the tubular sections acts as a pulley for one or more endless belts, and the other tubular section is non-rotatably mounted on a shaft or the like in order to transmit torque from the shaft to the belt or belts, or vice versa. It is customary to embed in the other tubular section a metallic sleeve which can be non-rotatably slipped onto the shaft so as to prevent any angular movements of the shaft and the other tubular section relative to each other.
A drawback of presently known articles of the above outlined character is that the bond between the metallic sleeve and the corresponding tubular section is unreliable, primarily due to the development of bending, stresses, especially rotating bending stresses, which tend to separate the external surface of the sleeve from the internal surface of the corresponding tubular section. The termination of a reliable bond between the sleeve and the corresponding tubular section of the article is attributable mainly, or to a large extent, to the development of bending stresses when the one tubular section is engaged by one or more endless V-belts or the like and the other tubular section is non-rotatably held on the shaft. It has been found that the sleeves become loose after a relatively short interval of use of such conventional articles so that the articles must be discarded in their entirety.
Attempts to prevent rapid separation of the sleeve include the provision of highly complex articles which are configurated and dimensioned with a view to reduce the likelihood of rapid or immediate termination of the bond between the sleeve and the adjacent tubular section. A drawback of such proposals is that the cost of the articles is unduly increased without guaranteeing the establishment and maintenance of a reliable and long-lasting bond between the metallic sleeve and the adjacent plastic material.